Friday, September 12, 2014

Here is an AI Refresher Course

(1)   Heat Detection                   (observing “estrus”)

The “best” sign is the mounting of the animal in heat.   She stands still for others to mount her.   Then our timing of insemination is easier, as you have standing heats for reference.   Breed cows standing at night the following morning, breed cows standing at morning after lunch, or if still heated up, wait to evening.     (The idea is to service at the end of standing heat—more on that later).

A beginning sign of estrus onset is the swelling of the vulva and the release of cervical mucus, which is shiny and clear.   The cow will be more active, restless, perhaps bawling a bit.   As the estrus progresses, the cow may try to mount other cows to draw attention.    Finally you see her standing to be mounted.

The stages of standing heat last several hours, so will be mixed in with feeding and other routines.    At the end of heat, cows start to refuse to be mounted (AI should occur right away, if not already).   The next day the cow will be quiet again—and within another day, you will likely see blood on the tail.

If not serviced, or if conception does not occur, you can expect her next cycle between 17 and 24 days later (21 days is the usual interval).      “False” heat signs are often seen mid cycle (ie, 9-11 days after a true heat) and are just a result of the hormonal production that stimulates the complete cycle.

(2)   Semen Handling            (protecting conception)

Your object in semen handling is to preserve unused semen by equipment and procedures that optimize the number of live sperm available in the straw after it is thawed for use.

Your liquid nitrogen semen tank is designed to maintain semen in a full state of suspended animation. Cryogenic temperatures (-320 F in the liquid, -140 F in the vapor) are adequate to maintain that state, but any time the semen straws/canes are moving above the vapor line in the neck of the tank (or between tanks) molecular movement from warming can begin.   

Transfer of semen canes should occur within a ten second interval.   A similar eight second time limit is “the rule” on removing the straw you are ready to thaw for breeding—to protect the straws you are NOT ready to use.    (If you do not get the straw you want in eight seconds, put the cane and canister back in the bottom of the tank, let it cool down 30 seconds, then lift it up and try again.)

We find the canister in which the sire we wish to use is stored.   You can hold the canister within the neck of your tank, by light pressure on the fiberglas stem, with the same hand that holds the cane steady (with thumb and forefinger) while you remove a straw.    Then (1) drop the cane down into the canister, (2) drop the canister into the neck, (3) put the removed straw in your thaw water, (4) set the canister in its hanger, (5) plug the tank neck.     The removed straw is being thawed, it is of secondary importance to the straws returning to the safety of your semen tank—thus the logic of the order given above.

Why thaw in warm water??   Because it is likely the semen you have was collected at multiple locations and with different extenders (fluids added to protect the sperm cells through freezing and thawing).   It is known that “pocket thaw” seems to work with milk extender semen, but can damage egg yolk, citrate, and soybean oil extended semen.    But warm water thaw works equally with ALL semen straws.  

(3)   The AI technique        (rectal palpation, cervical fixation)   

The thawed straw will be wiped dry, inserted into the barrel of a warmed AI gun.   The end of the straw is cut open, a sterile sheath is drawn over it (and secured by o-ring or spiral at the shank of the gun).  A dry paper towel is wrapped over the end, to reduce temperature shock, and slipped into your vest.

You will slide an OB glove over your left arm, fitting the hand to your fingers.   You will apply OB lube to the palm of your glove, and (if a soap lube, make a suds to clean the vulva surface) wipe lubricant on the vulva lips, then enter the rectum one finger at a time to relax and dilate the anus.   Any manure she pushes back to you, should be allowed to flow out, thus keeping the rectal rings in motion (more on that later).    Once the manuring stops, with your right hand, take an unfolded towel in the flat of your hand and make a single comprehensive wipe across the vulva surface, to clean the area for entry.

Taking the AI gun in your right hand, you now enter the vulva using a slightly uphill angle (to avoid an entry into the urethra, which drains the bladder—an area very sensitive to the cow and unconnected to her reproductive system).    You will find that pushing gently down against the vulva from inside with your left hand (folded into a fist) usually will spread the vulva lips apart to make a cleaner entry.

I then relax my left arm inside the rectum, while sliding the AI gun as far into the vagina as it will go easily.    In most cases (as the vagina is a funnel and only leads to the cervix) the gun will end up at a point in front of or slightly alongside the cervix.    I then work my left hand down to find the end of the gun and explore the tissue structures it has found, to detect the size, shape and angle of the cervix.

Keep in mind the entire reproductive tract—vagina, cervix, uterus body, uterine horns, and ovaries—are mounted on a membrane that is anchored to the pelvic bones, designed to allow stretching of the weight of the calf into the body cavity as pregnancy progresses.    So the cervix and uterus can move about, and we must be careful not to “bulldoze” what we are seeking over the edge of the pelvis into the body.

The cervix can be grasped roughly half around by lifting it off the membrane, and this allows you some control of cervix movement as you seek to guide the gun into its vaginal entrance.   The cervix feels like a “chicken neck”—you may sense folds (rings) that the gun passes through to reach the uterine body.

Once you pass the gun through the cervix, you will feel the tip coming out of the cervix.   You need to hold the gun in the uterine body, by placing your index finger over the tip, so it does not slide up into one of the uterine horns.    At this point, you grasp the plunger with your right hand, push the semen into the cow, then remove the gun, and finally remove your left arm.

Once your gloved hand is out of the cow, grasp the base of the vulva between thumb and finger, and as soon as you find the clitoris (buried in the fat tissue of the vulva base), flick it repeatedly.   If done with finesse and sensitivity, the cow will arch her back—at this point, her nervous system has been sent the signal that breeding has taken place, and will then initiate the steps to trigger ovulation.

(4)    How conception actually occurs  

Six to twelve hours after the end of standing heat (when you bred the cow), the follicle on one ovary will rupture and release its ovum (egg).   The infindibulum membrane catches it, and sends it up the fallopian tube, where it will meet the waiting sperm cells.    Sperm rub against the enzyme shell until one is able to penetrate and complete conception.    Over the next week, during cell division, it migrates to the horn and will attach to the uterine wall.    Over the next six weeks, it transitions to full fetal attachment.    

The miracle of life—celebrated each spring with the birth of calves

Nothing beats the sight of a herd of momma cows in green paddocks, grazing grass and nursing a full crop of calves.     The cattleman knows reward for the prior season’s time and expense for breeding those cows, and can predict his likely income.

But that means we need to be picking out sires, ordering semen, restocking our supplies and preparing for heat detection, maybe estrus synchronization, and breeding.

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